Hyperparameter estimation for satellite image restoration using a MCMC maximum-likelihood method

The satellite image deconvolution problem is ill-posed and must be regularized. Herein, we use an edge-preserving regularization model using a ? function, involving two hyperparameters. Our goal is to estimate the optimal parameters in order to automatically reconstruct images. We propose to use the maximum-likelihood estimator (MLE), applied to the observed image. We need sampling from prior and posterior distributions. Since the convolution prevents use of standard samplers, we have developed a modified Geman-Yang algorithm, using an auxiliary variable and a cosine transform. We present a Markov chain Monte Carlo maximum-likelihood (MCMCML) technique which is able to simultaneously achieve the estimation and the reconstruction.     

Evidence of thermally induced borehole elongation: a case study at Soultz, France

When they occur, borehole breakouts are considered strong markers of principal stress directions at depth. An innovative processing method for automatically identifying breakouts from ultrasonic borehole wall images has been developed. It has been applied to data sets from two deep, sub-vertical wells (GPK1 and GPK2) at the Soultz geothermal site in eastern France. In well GPK1, below 3 km depth, compression breakouts, with a 95°±7° azimuth, increasingly occur with depth. They result from time dependent compression failure at sub-critical stress levels and are indicators of the minimum horizontal principal stress orientation. However, in the uppermost logged section of well GPK2 (1.6–2.9 km depth), continuous borehole elongations share roughly the same azimuth with so called drilling-induced fractures (164°±18° and 175°±17° azimuth, respectively). Both features concomitantly vanish with depth, together with the amplitude of the thermal perturbation induced by drilling. It is proposed that these latter borehole elongations result from a pervasive, cooling-induced, tensile micro-cracking process prior to macroscopic failure localization. They are termed thermal elongations and are indicators of the maximum horizontal principal stress orientation. Had a simple logging caliper tool been used for this work, these thermal elongations might have been confused with classical compression breakouts. A simple criterion for differentiating compression breakouts from thermal elongation is proposed.     

Processing of yttria partially stabilized zirconia thermal barrier coatings implementing a high-power laser diode

Several studies have been undertaken recently to adapt yttria partially stabilized zirconia (YPSZ) thermal barrier coating (TBC) characteristics during their manufacturing process. Thermal spraying implementing laser irradiation appears to be a possibility for modifying the coating morphology. This study aims to present the results of in situ (i.e., simultaneous treatment) and a posteriori (i.e., post-treatment) laser treatments implementing a high-power laser diode. In both cases, the coatings underwent atmospheric plasma spraying (APS). Laser irradiation was achieved using a 3 kW, average-power laser diode exhibiting an 848 nm wavelength. Experiments were performed to reach two goals. First, laser post-treatments aimed at building a map of the laser-processing parameter effects on the coating microstructure to estimate the laser-processing parameters, which seem to be suited to the change into in situ coating remelting. Second, in situ coating remelting aimed at quantifying the involved phenomena. In that case, the coating was treated layer by layer as it was manufactured. The input energy effect was studied by varying the scanning velocity (i.e., between 35 and 60 m/min), and consequently the irradiation time (i.e., between 1.8 and 3.1 ms, respectively). Experiments showed that coating thermal conductivity was lowered by more than 20% and that coating resistance to isothermal shocks was increased very significantly.     

Exploring thermal spray gray alumina coating pore network architecture by combining stereological protocols and impedance electrochemical spectroscopy

Complex multiscale pore network architecture characterized by multimodal pore size distribution and connectivity develops during the manufacture of ceramic thermal spray coatings from intra- and interlamellar cracks generated when each lamella spreads and solidifies to globular pores resulting from lamella stacking defects. This network significantly affects the coating properties and their in-service behaviors. De Hoff stereological analysis permits quantification of the three-dimensional (3D) distribution of spheroids (i.e., pores) from the determination of their two-dimensional (2D) distribution estimated by image analysis when analyzing the coating structure from a polished plane. Electrochemical impedance spectroscopy electrochemically examines a material surface by frequency variable current and potential and analyzes the complex impedance. When a coating covers the material surface, the electrolyte percolates through the more or less connected pore network to locally passivate the substrate. The resistive and capacitive characteristics of the equivalent electrical circuit will depend upon the connected pore network architecture. Both protocols were implemented to quantify thermal spray coating structures. Al₂O₃-13TiO₂ coatings were atmospherically plasma sprayed using several sets of power parameters, are current intensity, plasma gas total flow rate, and plasma gas composition in order to determine their effects on pore network architecture. Particle characteristics upon impact, especially their related dimensionless numbers, such as Reynolds, Weber, and Sommerfeld criteria, were also determined. Analyses permitted identification of (a) the major effects of power parameters upon pore architecture and (b) the related formation mechanisms. This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials Park, OH, 2006.     

Effect of the doping time of the 1‐butyl‐3‐methylimidazolium ionic liquid cation on the Nafion membrane proprieties

Nafion membranes were prepared by incorporating in the polymer matrix the 1‐butyl‐3‐methylimidazolium (BMI⁺) ionic liquid cation at different doping levels. Increasing the doping time of the membranes with the ionic liquid results in increased incorporation of the BMI⁺ cation but a decrease in the bulk conductivity. The thermogravimetric analysis shows that the BMI⁺ cation incorporation increases the thermal stability of the membranes. The higher discharge efficiency of the fuel cell at 80°C was obtained by using Nafion membrane after 15 minutes of doping in the ionic liquid solution.     

Influence of cooling rate on microstructure and mechanical properties of a Ti–48Al alloy

The microstructure of a Ti–48Al alloy cooled after a solution treatment in the -field is influenced by the cooling rate. In order to characterize the lamellar structure and to know the values of ₂-volume fraction, width of ₂-lamellae, and interlamellar spacing, we developed a method of measurement based on an observation of laths in the scanning electron microscope. The study revealed the heterogeneous distribution of the lamellar structure in a commercial purity Ti–48Al alloy cooled from the -field at a rate of 35°C/min. The evolution of ₂-volume fraction with the cooling rate showed that the microhardness is determined by the quantity of ₂-phase. The values of yield stress also increased and were all the less scattered as the structure became more perfectly lamellar. Yield stress and interlamellar spacing are linked by a Hall–Petch relation.     

Effects of the smoking process on odour characteristics of smoked herring (Clupea harengus) and relationships with phenolic compound content

The relationship between smoking parameters and odour characteristics, evaluated by a trained sensory panel, were studied on smoked herring. In addition, a possible correlation between the content of 10 phenolic compounds and sensory perceptions was investigated. Five smoking techniques were applied, combining smoke production conditions, performed by pyrolysis of beech wood sawdust or by friction of beech wood log, with smoke deposition, either in a controlled kiln (traditional smoking) or by an electrostatic process. In the fifth smoking technique, a purified condensate of beech smokes was vaporised on fish fillets in the smokehouse. The time of smoking was 3 h for traditional smoking and the liquid smoke atomisation process and 12 min for the electrostatic method. The effects of three smoking temperatures (16, 24, 32 °C) were tested for both the traditional and the liquid smoke atomisation processes, as well as the effect of the position of the exhaust valve in the smokehouse in the case of the traditional method. Two different voltages were applied for the electrostatic process, 37 and 42 kV.     

Increasing temporal resolution of DSC perfusion MRI using the analytic image concept

Object  

Dynamic susceptibility contrast MRI (DSC-MRI) is increasingly being used to evaluate cerebral microcirculation. In this study, the use of the analytic image reconstruction (AIR), with the aim to increase the temporal resolution, is evaluated for DSC-MRI in small animals.     

pH-metric study of the setting reaction of monocalcium phosphate monohydrate/calcium oxide-based cements

Hydraulic calcium phosphate cements (CPCs) that are used as osseous substitutes, set by an acid–base reaction between an acid calcium phosphate and a basic calcium salt (often a phosphate). In order to gain a better understanding of the setting of the monocalcium phosphate monohydrate–calcium oxide cement that we developed and in the aim to improve its mechanical properties, the setting reaction was studied by pH-metry. The two methods described in the literature were used. In the first, cement samples were prepared then crushed after different storage periods at 37 °C, 100% RH. The powder was then immersed in pure water with stirring and the pH was measured after equilibration. In the second technique, the starting materials were poured into water while stirring and the pH were followed over time. The two methods gave different results. The first procedure provided information concerning the pH of the surrounding liquid following the partial dissolution of the cement components, rather than any information about pH changes during setting. The second method is more appropriate to follow the pH variations during setting. In this second procedure, the effects of different parameters such as crushing time, stirring rate, liquid-to-powder (L/P) ratio and temperature were investigated. These parameters may impact substantially on the shape and position of the pH=f(t) curves. One or three pH jumps were observed during the setting depending on the composition of the liquid phase. The time at which these pH jumps occurred depended on the pH of the liquid phase, the concentration of the buffer, the crushing of starting materials, the L/P ratio and the temperature. Good linear correlations were obtained (i) between the time of the pH jumps and the L/P ratio and the temperature and (ii) between the time of the first pH jump and the compressive strength and the final setting time of the cements prepared with different liquid phases. It may be assumed in view of these correlations that the results obtained in dilute solution may be extrapolated to the conditions of cement sample preparation and that the mechanical properties of the cement are directly related to the phenomena that occur at the first pH jump which corresponds to precipitation of dicalcium phosphate dihydrate.     

SAR image filtering based on the heavy-tailed Rayleigh model.

Synthetic aperture radar (SAR) images are inherently affected by a signal dependent noise known as speckle, which is due to the radar wave coherence. In this paper, we propose a novel adaptive despeckling filter and derive a maximum a posteriori (MAP) estimator for the radar cross section (RCS). We first employ a logarithmic transformation to change the multiplicative speckle into additive noise. We model the RCS using the recently introduced heavy-tailed Rayleigh density function, which was derived based on the assumption that the real and imaginary parts of the received complex signal are best described using the alpha-stable family of distribution. We estimate model parameters from noisy observations by means of second-kind statistics theory, which relies on the Mellin transform. Finally, we compare the proposed algorithm with several classical speckle filters applied on actual SAR images. Experimental results show that the homomorphic MAP filter based on the heavy-tailed Rayleigh prior for the RCS is among the best for speckle removal.